1. Field of the Invention:
This invention relates to an improvement in a document feeding apparatus adapted to automatically feed a document from a document feed tray onto a document glass plate in a reproducing machine or an image reading device and discharge the document from the document glass plate after it has been processed, and more particularly to a document feeding apparatus having means for feeding documents sheet by sheet by hand.
2. Description of the Prior Art:
In an image recording apparatus, such as an electrophotographic reproducing machine or an image reading device, an automatic document feeding apparatus (which will hereinafter be referred to as ADF) is used so as to efficiently carry out a preprocessing for an image processing process (copying process). This ADF is adapted to go into an ADF mode when a plurality of sheet documents are set on the document feed tray. In accordance with a copying start signal, the documents are sent sheet by sheet automatically onto a document glass plate, and they are discharged into and held in a document discharge tray automatically after an exposure step has been carried out.
The ADF consists of a document feed unit adapted to receive preset documents and send out the documents sheet by sheet at accurate intervals, a transfer unit adapted to transfer each document onto a document glass plate and stop the document in a document setting position accurately, and a document discharge unit adapted to discharge the document from the document glass plate and store the same on the document discharge tray after the exposure of the document has been completed.
There are two types of document feed units, i.e. a document feed unit of a lower side document feed system in which stacked documents are fed sequentially with the lowermost document first, and a document feed unit of an upper side document feed system in which stacked documents are fed sequentially with the uppermost document first.
The lower side document feed system is advantageous in that the documents to be processed can be stacked one on top of the other. However, power required for a document separating operation is several times as large as that needed in the upper side document feed system in order to withdraw the lowermost document, and stress on the documents increases accordingly. This causes the documents to be deformed easily. Especially, a document separating member soiled by pencil-written documents stains other documents, and the pencil-written information is likely to be erased or blurred easily. These problems occur more or less in the document separating and feeding operations in the upper side document feed system as well.
In general, the documents handled in an image recording apparatus, such as a copier have on their surfaces information printed in printing ink or written with a writing instrument, so that such documents have greatly different feed characteristics. Moreover, many documents have different forms, i.e., they include slips, leaflets, hand-written documents and drawings, and also documents having perforations, folds and wrinkles. Since it is necessary that the documents be fed so as not to be hurt, some kinds of documents prove to be unsuitable for an ADF application.
There are some cases where the ADF cannot be used due to the necessity of preventing the occurrence of soiling of documents during the document separating and feeding operation.
In order to take copies of these documents, it is necessary that a document be placed on the document glass plate without using the ADF, with the ADF as a whole opened in the same manner as a document holding plate (platen cover), and that the ADF be then closed to carry out a copying operation. This requires a great deal of time and labor.
In order to copy one sheet of document or a small number of sheets of many different kinds of documents or various kinds of documents of different sizes by using the ADF with the documents fed sheet by sheet by hand, it is necessary to press a copying button each time, so that the copying operations become troublesome.
A semi-automatic document feeding apparatus (SDF) adapted to feed the documents, which are inserted sheet by sheet by hand, onto a document glass plate automatically and discharge the document automatically after the copying thereof has been finished. However, the SDF is not capable of processing a large number of documents automatically and continuously.